Sensitivity of anthropometric techniques for clinical trials in ankylosing spondylitis.

To determine whether anthropometric techniques widely used for assessment of ankylosing spondylitis (AS) would be useful outcome measures in long-term clinical trials, 52 AS patients at the Royal National Hospital for Rheumatic Diseases were studied. All patients had well documented AS with a mean age of 38.1 years, and had been diagnosed for an average of 7.6 years. Measurements were taken before (B) and after (A) 3-week intensive inpatient physical therapy (PT). Short-term therapeutic effects (over 3 weeks) were significant (adjusted p less than 0.0001) for all five measures tested (chest expansion, finger-to-floor distance, height, lumbar flexion, and cervical rotation). Height (adjusted p less than 0.0001), finger-to-floor distance (adjusted p = 0.047) and cervical rotation (adjusted p = 0.012) diminished over the course of follow-up. Therefore, 3 weeks of hospitalization with intensive physical therapy produces measurable short-term change; minute but measurable change with treatment occurs even in long-standing AS; and detectable changes in physical measurements occur over a 5-year period even in long-standing AS. Anthropometric measurements are useful outcome variables for long-term clinical trials in AS, but the potential for improvement in clinical measurements in long-standing AS is predictably small.